Fig. 18.1
Data from the Portuguese national survey – Health Behaviour in School-Aged Children (HBSC) [60], including 3476 students with a mean age of 14 years. The mean BMI is plotted against sleep duration in week days. Noticed the marked reduction in BMI for sleep durations equal or longer than 8 h
Furthermore, other sleep variables and sleep behaviors correlate with increased obesity risk. In preschoolers parental presence when falling asleep and short sleep duration are associated with increased BMI [36]; in schoolchildren shorter sleep duration, high-screen or TV viewing time, and low socioeconomic status were associated with increased BMI [26].
Cardiometabolic risk in adolescents has however gender differences, since the differences in cardiometabolic markers are statistically significant for girls: increased cholesterol and high-density lipoprotein (HDL) occur predominantly in the subgroups who go to bed late and rose early and in those which are sleepy and tired at least once a week [37].
The opposite pathway is also at stake: obesity is a risk factor for sleep disorders in children and adolescents, namely, for obstructive sleep apnea syndrome (OSAS). The relation with OSAS is bidirectional, since OSAS associated with short sleep duration is a risk factor for obesity [38].
Gastrointestinal Disorders
Gastroesophageal reflux (GER) is the passive transfer of gastric contents into the esophagus due to transient or chronic relaxation of the lower esophageal sphincter [39]. It may be present since birth, occurring in 51 % of the infants, but it is problematic in 14 % of them [40].
The recumbent sleep position increases the reflux and sleep complaints are common, with the child crying when lying down or having frequent awakenings, especially after a meal; frequent vomiting, spitting, and regurgitation are usually alerting symptoms, together with wet burps and wet hiccups and inconsolable crying after eating. Suffocation is a rare but possible complication, and swallowing fits, during which the agitated child turns around in bed, sweating, spitting, with associated swallowing movements, can justify the differential diagnosis with epileptiform seizures.
The association with OSAS is frequent; gastroesophageal reflux disease (GERD) is among the comorbidities of OSAS occurring in 30 % of the cases [41]; it is a predictor of complications of adenotonsillectomy [42] and is usually associated with residual OSAS after an adequate treatment [43]. GERD may also be associated with asthma and with obesity in children.
Hematologic Disorders
Sickle Cell Anemia
Sickle cell disease (SCD) is an inherited blood disorder associated with hemoglobin S; the red cells have a characteristic donut shape (the drepanocytes) and lack plasticity, and as a consequence they can block the blood vessels, provoking acute pain syndromes, bacterial infections, and tissue necrosis [44, 45].
The impact upon sleep is serious, since several factors contribute to it, namely, the pain episodes, anemia, and sleep-disordered breathing. Children have significantly higher rates of parent reported SDB and night wakings [46, 47], together with objective demonstration of polysomnographic features of OSAS [47].
Elevated periodic limb movements of sleep (PLMS) are common in children with SCD and are associated with sleep disruption and symptoms of restless legs syndrome (RLS) [48].
Thalassemia
Thalassemia is an inherited, mostly autosomal recessive, blood disorder associated with abnormal formation of hemoglobin, which results in abnormal transportation of oxygen and destruction of red cells. It predominates in Mediterranean countries (European, West Asia, and North Africa), South Asian countries, and Maldives.
Besides anemia it may be associated with other complications, namely, slower growth rates, bone deformities, and cardiovascular disorders. There are alpha, beta, delta, and combined variants of thalassemia.
Symptoms may develop with different severity levels, but they are present since early life. Children and adolescents with beta-thalassemia have increased number of arousals during sleep which is partially due to the presence of periodic limb movements of sleep; a similar picture occurs in sufferers from congenital dyserythropoietic anemia type 1 [49]. Furthermore, children with thalassemia have an estimated prevalence of OSAS of 8.3 %; sleep apnea occurs predominantly in children with high serum ferritin levels; furthermore, snoring and adenotonsillar lymphoid hyperplasia should be considered as alert factors for the presence of OSAS [50].
Chronic Pain Syndromes
Chronic pain in children and adolescents may be a consequence of another disorder, as it is the case for juvenile idiopathic arthritis (JIA) and sickle cell disease (SCD) or the major symptom of a specific disorder [51], as it is the case in chronic idiopathic headaches or fibromyalgia.
The relation between sleep and pain in pediatric populations has been described by Lewis and Dahl 1999 [52]; the relations are bidirectional: pain interrupts sleep, and the interrupted sleep induces a dysfunctional cascade affecting emotional, immunologic, anti-inflammatory, and somatic balance, which by themselves increase pain. The model of Valrie et al. includes also disease stage, sex, race/ethnicity/culture, and socio-contextual factors [51].
The prevalence of chronic pain in pediatric community populations is very high, varying between 25 and 40 % [53].
Poor sleep is a common comorbidity; sleep can be affected by the presence of nocturnal pain, by the existence of other symptoms of the underlying disorder, by the required medication, or by the eventual hospitalizations; sleep disturbances can include bedtime resistance, increased awakenings, poor sleep hygiene, and the presence of SDB and/or parasomnias [51].
The behavioral, emotional, and cognitive dysfunctions of poor sleep and the consequences upon school achievement and family equilibrium are well known and tend to increase the severity of the chronic pain condition.
More detailed descriptions will be given for headaches, chronic muscle skeletal pain, and fibromyalgia.
Headaches
In children and adults the relationships between headaches and sleep are mutual.
The links, headache sleep links, are related to common neurophysiological, neuroanatomical, and genetic substrates [54].
The prevalence of headache increases from childhood to adolescence; it is similar in both genders before puberty, but afterward it is higher in females.
During adolescence frequent and chronic headaches are a common issue, affecting 22–32 % of the teens [55–59]. Sleep deprivation [60], sleep habits, and sleep disorders [61–64] are among the important comorbidities of chronic headaches.
Chronic Muscle Skeletal Pain Complaints
The prevalence of neck and shoulder pain is higher in girls; the risk factors are family history, school furniture, long sitting time, extended computer use, insufficient rest time, short sleep duration, transportation type, schoolbag weight, and smoking [67].
The prevalence of pain in the back, neck, and shoulders is high in adolescents and increases with sleep deprivation [60, 68, 69] and with irregular sleep schedules across weekdays and weekends [60].
The relations between chronic pain and insomnia are mutual, with insomnia being a risk for pain chronicity, while pain, poor sleep hygiene, and higher depressive symptoms are the main risks for insomnia persistence [70].
Fatigue and Fibromyalgia
Fatigue is rather frequent among children and adolescents [60] and occurs often associated with sleep disturbances [71, 72]. The risk factors for fatigue with poor clinical outcome are sleep problems, somatic complaints, blurred vision, pain in the arms or legs, back pain, constipation, and memory deficits, while the indicators of a good outcome are male gender and a physically active lifestyle [73].
The diagnosis of fibromyalgia in young ages is currently difficult due to the unspecific or vague complaints, but the prevalence of juvenile fibromyalgia syndrome (JFS) is relatively high, affecting 2–15 % of the children, being higher in girls and increasing after the puberty.
The symptoms include sleep difficulties in initiating and maintaining sleep, non-restorative sleep, generalized musculoskeletal pain, and daytime fatigue [74]; furthermore, there is a negative impact upon quality of life, increased rates of depression, and higher likelihood of missing school. Polysomnographic data of these patients demonstrates longer total sleep time, decreased slow-wave sleep, prolonged REM latency, and increased sleep fragmentation; actigraphy demonstrates a reduced activity during daytime [75].
The genetic components of fibromyalgia are currently described [76]; this together with the increased risk due to stressful events during childhood explains its relevance in young ages.
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